Maggin started working as a professional writer in his teens, selling historical stories about the Boer War to a boys' magazine. He wrote the comic story "What Can One Man Do?" for a class while in his junior year of college. When it was given a B+, Maggin disagreed with the assesment and sent his script in to DC Comics. It was passed around the DC offices and Neal Adams chose to illustrate the script. Though the initial grade was not corrected, Maggin became a writer for DC selling his stories to fund a Masters degree in journalism. He became the principal writer for Superman, where his innate understading of the principals of heroism, mixed with imaginative stories kept the iconic character popular for over 20 years. He also wrote for Green Arrow where his sense of humour was allowed far more freedom in the loose dialogue of the main character.
He wrote hundreds of comic stories, television scripts, stories for film, animation and journalistic pieces. He wrote two Superman novels: Last Son of Krypton and Miracle Monday, both considered classics by fans. He served as an editor for DC comics for a time and has also raised horses, run for public office in New Hampshire, taught at various high schools and colleges as well as ski resorts, wrote stories for Atari games, and has worked on websites.
Due to the fact that comic book scripts tend to favor the exclamation mark as the punctuation of choice Maggin was in the habit of using them instead of full stops. Out of habit, he once signed his own name Elliot S! Maggin and the distinctive rhythm of the name was enjoyed by editor Julius Schwartz who insisted that would be how the name was to be written thereafter.